rickets is a nutritional disorder that can develop if you do not get enough vitamin d calcium or phosphate rickets leads to poor functioning of a bone s growth plate growing edge softened and weakened bones stunted growth and in severe cases skeletal deformities
Hence, a 20-year period of the patent usually gives manufacturers a chance to recoup the cost of developing a new drug. When a drug patent expires, any pharmaceutical company can manufacture and sell the drug. A drug, which is produced and distributed without patent protection is called a generic drug.
US patents with a filing date before June 8, 1995 provide protection for up to seventeen years counting from the date of grant (the date given with reference numeral 45), or 20 years from the filing date, whichever expires later. However, the patent holder is required to pay maintenance fees to keep his patent valid. In most European countries, these fees are yearly. The USA requires maintenance fees to be paid at 3.5 years, 7.5 years, and 11.5 years after issuance. If the holder does not pay a maintenance fee, the patent becomes abandoned.